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Did anyone else taste purple for a moment there?

Chemistry microkits must be very profitable, given their widespread distribution [1]. They certainly look very pretty, and I think a set of erlenmeyers (3, 2, and 0.75mL) would look awesome on a kitchen shelf, by the window. But as far as organic chemistry is concerned I’ve never found the bulk of microscale glassware practical [2], largely due to the joints. It’s a bit of a catch-22. If the reaction vessel has a joint that fits well with the bulk of our lab equipment (14, 19, or 24) it will be top-heavy, just itching to fall over.  If the joint is well proportioned (10 or 12, generally), the vessel won’t connect to non-microkit glassware without special adaptors, which are usually bigger than the flask itself.

The best solution I’ve found is to use 4mL threaded vials. They’re cheap, semi-disposable and the perfect size for any reaction involving 3mL or less of solvent (generally 0.3g and down) [3]. We buy white caps with a PTFE membrane insert, which makes it easy to label both vial and cap, but still allows for argon balloons and injections under inert atmosphere. The insert is essentially a chemical resistant septa, with a seal strong enough to hold most organic solvents for months at a time [4].

Vials have a very narrow base, which makes it easy to run several reactions off the same stirrer (my record is seven, with the vials held together with a rubber band). However, the only stir bar I found that spins well is the flea micro. Only 8mm long and 1.5 thick, the micro stir bars are almost impossible to keep track of. I’ve taken to storing them in a specially marked vial, drying with a kimwipe after each use and limiting their time in use. I still lose one every week or so.

I covered concentrating solutions in 4mL vials in my very first post, so next we’ll look at connecting to other types of equipment (ie. reflux condensors).

[1] For a data point of one, our lab has three of them, all collecting dust in a box somewhere.

[2] You can have my micro Dean-Stark kit when you pry it from my cold, benzene-soaked hands.

[3] With the 20mL/5dram vial replacing the 25mL RBF. We have several cases of these from an HPLC purchase a few years ago, and they’re surprisingly useful. Concentrating samples within them can be problematic, but there’s no issue if you have a direct workup.

[4] I have some TLC solutions that were made back in 2010. The compound might degrade, but the methanol isn’t going anywhere.

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